The present invention relates to brake anti-squeal systems for vehicular wheel assemblies.
It is well known that objectionable levels of noise are generated in brake assemblies, such as those utilized on trucks and other large vehicles, wherein the brake drum is substantially concentrically mounted within the plane of the wheel rim. Because the brake drum is not directly attached to the wheel rim, the drum is caused to vibrate independently of the wheel rims when the brake shoes are pressed against its interior surface, so that highly audible noises and squeals are produced.
A number of attempts at eliminating the production of such noise have been made. One such attempt is shown in U.S. Pat. No. 3,163,469 where metal spring clips are inserted between the outer surface of the brake drum and the wheel rim. The clips are intended to dampen the vibration of the drum by connecting the drum and rim. However, in this construction it is difficult to predetermine the tension necessary for the spring clip to have a meaningful connection with the rim and drum, and the degree to which noise is abated is a hit and miss process. Further, after only a short period of vehicle operation, the vibrations and stresses created during road use reduce the efficiency of the spring clip resulting in its eventual dislodgement. A still further disadvantage lies in the fact that the outer surface of the brake drum has to be provided with one or more undulations in order to hold the spring clip in place.
Another attempt was made in U.S. Pat. No. 2,369,195 where a dampening block was attached by a bolt mechanism to the frontal edge of the brake drum so as to be permanently fixed thereto. The dampening block extends radially outwardly in contact with the side flange or surface of the tire rim and is resiliently biased against this flange. This construction has the disadvantage that the dampening occurs only at the flange which is not subject to any braking pressure. Thereby, only a limited amount of dampening occurs.
A further attempt at dampening the vibration of the brake drum is shown in the patents to HOLE and HOLE et al U.S. Pat. No. 3,186,766 and U.S. Pat. No. 3,136,557, respectively. In each of these patents, a similar device is shown which comprises a set of metal plates one attached to the wheel rim and the other attached to the outer surface of the brake drum. The two plates are also attached to each other by means of a bolt and slot mechanism so that they can be relatively adjusted in the radial direction to vary the pressure applied by the plates against the rim and the brake respectively. This device is disadvantageous in that it forms a more or less permanent fixed connection between the wheel rim and the brake drum, since part of the mechanism must be welded to the brake drum.
The present invention has as its object the production of a brake anti-squeal apparatus for large vehicular wheel assemblies which avoids the disadvantages of the prior art and which provides a more simple and more effective means for eliminating noises arising from the brake drum.
It is a further object of the invention to provide a brake anti-squeal system which is usable when needed and selectively adjustable in pressure against the brake drum and tire rim in accordance with the size and other vibrating characteristics of the brake drum, and which will maintain such pressure even over extended road travel.
These objects together with other objects and advantages will be forthcoming from the following disclosure of the illustrative forms of the present invention.